Tracking long-term benthic recovery at a disused marine aggregate extraction site using monitoring tools developed for the marine aggregate industry

Structural recovery of sediment habitats is predicted following removal of pressures from marine aggregate extraction, but long-term investigations are lacking. We demonstrate recovery of an extraction site to comparable control conditions for sediments (after 11 years) and macrofaunal assemblage (after 15 years) using the Mahalanobis-test and Faunal Cluster ID shiny R applications (available via https://rconnect.cefas.co.uk/onebenthic_portal/ ). Similar levels of annelid diversity were observed between impacted and control sites eight years post-dredging while bryozoan diversity at the impacted site did not reach control conditions. The observed changes in macrofaunal structure and cluster group allocation are likely in response to resumed dredging activity nearby. The present study informs our understanding of benthic recovery following intensive aggregate extraction and validates current monitoring tools. Further confidence in these and the underlying approach will be provided through collection of seabed recovery data from additional sites, representing the full range of environmental conditions and dredging practices. • Sediments at former UK aggregate extraction site returned to control conditions after 11 years. • Macrofaunal assemblage was similar to reference conditions after 15 years. • Bryozoans showed evidence of recovery but did not reach reference conditions. • Macrofauna assemblage responded to nearby test dredging. • OneBenthic Faunal Cluster ID and M-test tools align well with our analyses.